Melting furnace



Jan. 2, 1923. 1,440,515.

G. WELLMAN ET AL.

MELTING FURNACE.

FILsD MAY 11. 1920. a suus-SHEET 1` @wfmmm Jan. 2, 1923.

H. G. WELLMAN ET AL.

MELTING FURNACE.

FILED MAY 17, 1920.

3 SHEETS-SHEET 2.

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0MM. 6a p//v MLM.

Jan. 2, 1923. 1,440,515. H. G. WELLMAN ET AL.

MELTING FURNACE.

m50 MAY 17. :920. a sHrzErs-snzf 3.

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Patented dan. 2, 1923.

liiiTED STriTES PATENT OFFCE.

EOLLEY G. WELLMAN ND CHARLES D. GIL? 1N. OF CLEVELAND, 01H30.

MELTNG FURNCE.

pplication filed ey 17,

To u!! iff/mm. if may courent:

Bc it known thut we. lloLLi-: (iv Einnahme und Guinnes- D. (lumix.citizens of the Vnitcd ritutes. residentsofCleveland.county of Cuyahoga.and State of hio. have invented new and useful Improvements in MeltingFurnaces. ot' which the Jfollowing is a specification. the principle ofthe invention being hei-cin explained und the liest mode in 1U which wehave contemplated applying: that principle, so us to distinguish it fromother inventions.

(lor invention relates to furnaces, and particularly to devices ot' thischaractcr adopted to melt non-ferrous metals for nothing ln'onzc. brassund similar castings. 'lhe purpose of the invention is to provide afurnace in which las or oil run be utilized as the heating medium.combined with electrical heating. Thr object is to secure the economyot' installation und operation possible iu `gas or oil heating. andalso. et the necessary stage in the melting'. secure the neutral orreducing atmosphere in the furr, nare and the ease oi control in theheat, supplv. possible through electric heating. Spccilically. we houtthe charge to o point where it approaches the oxidiaingr tcnipern turcby menus of thi` ,uns or oil heating'. and then finish the melting bymeans nt electric heating. Also. we utilize `the heating effect of theras or oil not only to raise the temperature o'l the charge. hut also tobring un electric heating element to a'teinperature which will require:i much smaller variation in voltage than is usually required for theoiicrution ol :i furnace of the resistance type.

The annexed drawings and the following description set vforth in detailcertain means n embodying our invention. the disclosed means. however.constituting.r but unc of thc various mechanical forms in which theprinciple of the invention um)` hc applied.

li said annexed drawings:

5 ldigznre 1 represents u vertical. longituflinul ser-tion of ourimproved furnace:

Figure 2 represents ii plan View of the saine:

Figure 3 represents u fragmentary transverse. vertical section tulcen inthe plane in-v dicated hv the line lll-dill. Figure l:

Figure 4 represents n horizontal section ot another foi-1n of ourimproved furnace: one of the arc design. in which electrodes are 5 usedfor the electric heating; and in which i520. Serial lio. 352,062.

view the arrangement is shown during the heating by gas or oil;

Figure represents a view similar t0 that, of Figure L showing theconditions during! the electric heating;

Figure (l represents a vertical section of thc forni or' furnace shownin Fighrcs Land token in the plane indicated by the line ll--VL FigureFigure T is a diagrammatic view. showin-,fr the adapta tion of theinvention. when utilized lFor several small units grouped ou onetransformer. nuto-transformer or generator. for making different alloysat the saine time.

Referring to the annexed drawings: There is indicated hy the ordinal 1 ufurnace body of heat-resistin r material rotatably mounted in bearings72 y means of trunmons 2, the rotation or tiltingr `of the furnace beingeffected through a suitable gear 3, pinion 4 and hund wheel 5. Thefurnace 1 is formed with a chamber G within which is disposed a crucible7 adapted to hold the charge B. When it is desiredto discharge thecontents ofthe erucible 7, the' same is effected through the. spout il.We do not wish, howevere to limit ourselves to the use of a erueible.Ysince, if desired. the metal can be melted upon u. hearth. Two flexibleconductors 10 and 11 are sho-wn connected respectively at the points 12and 13 with any lsuitable main circuit. removable top 14 is provided Forthe furnace 1. which is disposed adjacently the top of the crucible T.the electric circuitpassing through said top und also through the fieldol a solenoid 15. The conductors l() and ll have suiiiclent slack toallow for the necessary movements of the furnace 1 and `the top 14. Thespecific path of th circuit through the. top 14 includes two carbonelectrodes 16 und 1T. a heating element 1S and two terminals 19connecting the electrodes. respectively. to the conductors. The heatingelement 18 is preferably a carbon compound'having;r a negativetemperature resistance coefiicient so that its olnnic value is greaterwhen cold than when it is hot. The top is removed to one side of thefurnace when charging, by means of attaching the chains of a crane tohooks 45. it will be noted that "che heating element, 18 is disposed inthe vicinity 0f the chamber G, so as to be heated b' the gas or oil` butis protected from oxi ization by any suit able means, the means hereinshown being e.

small section 20 of the top 14, which top is huilt of refractorymaterial.

The solenoid 15 has a plunger 21 formed on one side with teeth 22adapted to mesh with a pinion 23, keyed to a shaft 24. To this shaft 24are also keyed upon opposite sides of the furnace 1 two bevel gears 25and 26. The bevel gear 25 meshes with a bevel gear 27 keyed to a shaft28. This shaft 28 is connected to a valve 29 controlling the airfurnished to the mixer throu h air line 31. The gas or oil is controlledy the valve 30 having connections with the fuel line 32` Check valves 33are provided in each of the lines 31 and 32 to prevent air from backingup into the gas or oil pipes, or vice veisain the event that one of thevalves 30 or 29 is closed. The mixer and burner diiecting the flame intothe chamber 6 is indicated by the ordinal 34. The bevel gear 26 mesheswith ai bevel gear 35 keyed to u shaft 36 which in turn is secured tothe waste outlet valve 37.

It is a parent from the foregoing dev Scription t at the early heatingof the charge 8 by the gas or oil from the burner 34 will gradually heatthe element 18 decreasing the ohmic value of the same, so that anincreasing amount of current can betransmitted through the electriccircuit, tbesolenoid plunger 2l gradually being drawn into the coil 15,which action, through the teeth 22, gear 23, etc., is utilized gradualito turn oil' the s or oil at the valve 30 an to close the outet 36, sothat the heating medium rudually changes over from oil or gas to eectricity.

vWe have provided adjustments whereby the amount of increase of currentnecessary to effect n certaindrop in the gas or oil can be varied. Also,it will be noted that we have keyed a crank 89 to the end of the shaft24, upon which crank is hung a weight 38, whose position can beadjusted. For

controlling the drop in the gas heating, we

have provided adjacently the bottom of the solenoid plunger 21 a seriesof various sized weights 42, 48, 44, etc., which can be picked up atpredetermined positions by the plun `ger 21, whereby the necessaryelectric force to pull the plunger 21 into the coil 15 can be set asrequired. Also, the conditions can thus be changed or adjusted so as torequire varying amounts of current to lift the plun- Iiger 21 throughdifferent parts of its stroke. The differential in the pull of thesolenoid is equalized by the differential in the pull of the weights. Inorder that, if the electric current is unexpectedly interru ted, theplunger 21 may not drop away rom the coil 15 and thus op? up the valves29 and e a 30, we have provi paw] 41 adapted to co-operate with ratchetteeth 40 formed u lon the side of the plunger 21 o posite to trat uponwhich the teeth 22 are ormed` Referring particularly to Figures 4, 5

und 6, there is therein disclosed a-form of furnace preferably of therocking type, de signed to melt the charge upon a hearth, and in whichthe electric heating is edected by means of striking and maintainin anare between two electrodes 53 and 55. he fur nace wall is indicated bythe ordinal 46 and a feed mouth for the same by the ordinal 47, thedschar @out being indicated by 48. Two sets o doors are provided, 52 and54, within which are mounted the electrodes 53 and 55 respectively, and49 and 50, within one of which a gas or oil burner 5l is mountA ed, andwithin the other of which is formed a discharge outlet 50 for the wastegas products. As illustrated in these heures,

the necessary heating by gas or oil is effected by means of closin thedoors 49 and 5U and then, when it is esired to change over to theelectric heating, the doors 49 and 50 ure opened und the doors 52 and 54containing the electrodes are closed. The electrodes *are then adjustedto strike the desired arc.

Referring to Figure 7. a diagram of an arrangement is shown wherebyseveral smul] furnaces may be grouped on one transformer,auto-transformer or generator, to produce different alloys. Due to thediversity feature of the load, 1t will be possible to make thecontinuous capacity of the immediate source of ower much smaller thanthc combined pea loads of the various furnaces. There is indicated bythe ordinal 56 an alternating current circuit, 57 denoting a switch and58 an auto transformer, which furnishes differential voltages to theconductors 59, (30 and 6l withrespect to the conductors G2. The electricheating elements or resistors are indicated by the ordinals 63, 64 undG5, and the several switches hy the ordinnls 66, 6T and 68. Regulatingrswitches are indicated by the ordinals 69, T() and Tl. so that anyparticular furnace can be supplied with roltage 59-62, 60-62, or (3l-62.This arrangement reudily lends itself to nu economical and exibleinstallation for u group of furnaces.

Our improved furnace will be found of particular service in smallplants, where, due yto the non-continuity of operations, the shuttingdown of the electric heating necessitates a re-heating of the furnacebefore it becomes effective, when next it is desired to utilize thesame.

It is not'necessary to interconnect the ,uns and oil and electricheating!I in the manner which we have described, nor to utilize theelectric current during the heating by gus and oil. The two forms ofheating may be utilized absolutely separately, as. for instance,illustrated in Figures 4. 5 and 6. The se arate and independent heatingalso would e feasible with the apparatus shown in Figures 1, 2 and 3.

The methods of operation would be varied llO for melting various kindsof materials, but for making castings out of brass or bronze ingots, theoperation would be about as follows:

The charge is placed in the crucible after first moving the top 14 toone side and the oil or gas burner then lighted. A constant potentialwill be connected to l2 and 13. The proper weights 42. 43, 44, ete.,will be placed in the solenoid mechanism, these weights having beendetermined by past experience in melting the same metal. During the`early stages of the heating, the flame will be controlled by theoperator by means of valves of the usual kind (not shown). At first, thecurrent through the resistor 1S will be negligible, but as the furnacebecomes heated, the ohmic value of the resistor will decrease. thusallowing a greater flow of current, which in turn will still furtherheat the nresistor, alllowing more current to flow. `If it is desired,the current need not be thrown through the resistor until the latter hasbeen well heated and the charge has nearly reached the meltingcondition. The solenoid regulating weights. 42, 43 and 44, will be sochosen that as the charge approaches the tempera-ture where oxidationbecomes a serious facto-r, the resistor 1S will have been sufficientlyheated to allow the solenoid plunger .21 to be lifted by the resultingcurrent, this lifting being done in one or several stages by the meansof one or several of the weights 42, 43, 44, as may prove desirable.This lifting of the plunger 21 will, of course` shut off the air andfuel valves 29 and 30 and close the waste gas valve 37 by one or severalsteps so that the source of heat will immediately or gradually becomeentirely electrical and the oxygen from the outside Will be cut ofi'.Heating will then proceed as in the case of an ordinary electric furnaceof the resistance type.

Almost any combination of automatic control for this electric heatingcan be installed, ranging from a simple overload circuit breaker, whichcan be set to interrupt the current when the latter reaches apredetermined point, to a more or less elaborate arrangement ofcontactors controlled by a pyrometer, and arranged to increase ordecrease the voltage by small steps in order to hold the finaltemperature constant. It should be noted, however, that any sucharrangement need cover only a comparatively small range of voltage owingto the pre-heating of the resistor; whereas, in the straight electricfurnace using this'type of resistor, a voltage range of as high as fourto one may be necessary in order to obtain the desired results. Thisnecessary range of voltage greatly increases the cost and complicatesthe auxiliary apparatus. Of course, it will be well known to thoseskilled in the art that compressed air and oil or gas are available inmost foundries and are in any event readily and economically provided.The automatic control of the fuel supply, as well as of the electriccurrent, may be dispensed with in cases where original cost is a seriousitem, and where the furnace may readily be kept under supervision. Inthe event that metals of various melting point-s are to he combined inthe furnace, the original charge can consist of the metal having thehighest melting point., and the automatic device may be set for suchmetal. Yhen it reaches the proper temperature. the cover 14 may heremoved and the other metals added, the electric` heating heiligcontinued as long as may he desired. i

The operation of the arc type of combination furnace shown in Figures 4.5 and 6 will be somewhat similar to that of the resistor type exceptthat the automatic change from fuel to electric heating would requiremuch more complicated apparatus and therefore is probably not desirable.This is due to the fact that the electrodes must necessarily heprotected from the flame of the burners unless they be withdrawn by somesuch device as shown in said figures. The melting of the charge in thisfurnace, therefore, consists in pre-heating the charge to a desirablepoint by means of closing the fuel doors 49 and 50, and then replacingsaid doors with the electrode doors and 54, striking an arc between saidelectrodes and maintaining the same for the desired period.

Either the type of furnace shown in Figures l to 3, or the type shown inFigures 4 to (i may be operated entirely with fuel or entirely withelectricity. This is a very desirable condition, inasmuch as alloyswhich oxidize slightly may thus, if desired. be melted entirely withfuel, while those which oxidize particularly easily can be meltedentirelyI by electricity. Furthermore, a failure either of the fuel orelectric power would still leave the furnace in commission.

lnsofar as the desirable features of electric heating are concerned, itshould be kept in mind that the electric type of furnace is graduallyreplacing the crucible and other processes, so that. although untilrecently used largely for the melting of silver and bearing metalalloys, it is now used for brass of all kinds, aluminum` various alloysand other materials. New non-ferrous combinations and new uses for thecommon nonferrous metals and alloys are constantly developed, for whichthe use of the electric heating feature of our furnace is verydesirable, at the same time preserving for the early stages of themelting the low cost of operation possible in gas or oil melting.

le are aware of the fact that it is not new to heat preliminarily by gasand later by electricity in the same furnace or cham- El I) llt titl

her. and we do not malte claim to any such conihination ot' apparatus.(hir invention relates to fuel and electric heatin"` and meansintcrconnecteil so that the operation of one is a tl'ected hy the other:or the use ot' an electric heating' element l1a\'in; r a negatiyctemperature resistance coetticient and disposed within the heating' areaotl gas or oil: or the use oll jas and electric heating means sointerconnected as to he recipro rahly replaceahie in thtI furnacechamber; or the use of a source ol' electric energy snpplyin; r Variousvoltages conihincd with means for selectively heating charges in variousfurnaces with the desired voltages from said source ot' electric energy.1We are also adiiscd that glas and electric heating hare heen comhinedin a two-furnace method. or in methods in which the hearth is positivelyremoved from an area in which its cfnitcnts are suhjected to gasheatingy to an arca in which it it is suhjected to electric heating'. hmour claims relate to a onet'nr nace method in which the furnace ismaintained in a tifo-d position.

7What we claim is:

t. ln a meltingr furnace, the comhination ot a chamhcred furnace hodyforming a rereptacle hir the charge; means tot' heating the charge with`as or oil including' means tor controlling' said heating; and means forheatin; if the charge electrically includingr means for controllingrsaid heating` said two sets ot' controlling means heilig interconnccted.

2. in a meltiim` furnace. the comhination ot' a rhamhered Vfurnace hotlyforming;r a receptacle for the charge; means tor heating' the chargewith gras or oil; and means l'or heating the charge eh-ctrically. saidtwo sets ot heatilr;T means being' interconnected so that an ette: tireincrease in the electric heat intr means results in a decrease in theiras or oil herding' means.

it. ln a melting' furnace. the comhination ot' a chanihercd furnacehod)I fortuin;r a re ccptacle for the charge; means for heating `thecharge with gas or oil; and means for heating' thc charge electricallyin the same hcating r area` said two scts of heating means heine'interconnecttal so that an ctiectiye increase in the electric heating'means results ina decrease inthe glas or oil heating' meansl. `In amelting furnace. the comhination ol' a chanihered furnace hody torminrgra reccptacle for the charge: means t'or heating the charge with gas oroil; lneans for heat ing' the charge electri 'ally. said two sets ofheating' means heiner interconnected so that an effective increase inthe electric heating1 means results in a decrease in the ,Q'as or oilheating means: and means for yaiyingr the ratios hetween said increaseand decrease.

5. In a melting furnace. the combination of a chamhered furnace hodyforming;f a receptacle for the charge: means for heatingr the chargewith gas or oil; means for heat.- ing the charge electrically, said twosets of heating;r means being iutereonnectwl so that an etfectiyeincrease in the eleetric heatiner means results in a decrease in the gasor oil heating means; and means for varying the ratios hetween saidincrease and decrease in different portions ot' the heatingr range.

(i. In a meltingr furnace. the combination ot' a chamhered furnace hotlytorinimgr a receptacle for the charge: means for heating' the chargewith gas or oil; an electrical heating' element disposed within theheating' area of said gas or oil and haring' a negfzr tire temperatureresistance coefficient; and means for heatimgf the charge electrically.said element heine' disposed in the circuit ot' said electrical heatingmeans.

T. ln a melting furnace, the combination` ot' a chamhered furnace hotlyforming a receptacle for the charge: means tor heating tht` charge withgas or oit: an electrical hcating element dispostai within the heating'area of said gas or oil and having a negative tem peratnrc resistancecoetlieient; means for heating the charge eleetrieatly. said clementheine' disposed in the circuit of said eter:- trical heating means; andmeans influenced hy a gradual effective increase in the electric heatingto ei'eet a corresponding decrease in the ras or oil heating.r means.

t4. lin a melting furnace, the conihination ot' a chamhered furnaeebody: a erucihle disposed therein; a top ot' refractory material forsaid hotly disposed adjacently the top ot said .-rncihleg a heatingelement iinhcdded in said top adjacently said crucihle and harin;i anegative temperature resistance co ctiicicnt: an electric circuit withinwhich said element is contained; means furnishingr heating gas or oil tosaid chamber: and means connected to said last-mentioned means and .saidcircuit and adapted to reduce the heating value ot' said gas or oilcorrespondingr to the increase in the electric circuit.

E). ln a melting' furnace, the comhination of a chamhered furnace hody:a crucihle dispt'ised therein: a top ot' refractory material for saidhody disposed adjacently the top of said crueihle: a heating: elementimhedded in said top adjacently said crucihle and havin? a negativetemperature resistance co-eieient; an electric: circuit within whichsaid element is contained: means t'urnishing heating gas or oil to saidchamber; a solenoid forming part of said electric eircuit: valves in thegas or oil line and in the chaniher waste outlet; and means connected tosaid valves and the plunger of said solenoid.

lit)

10. In a` melting fuirizii'eE lli@ i'fiiiiliiiiiitiiiii of a Chaiiiberedfurnace body fni'iiiinggj i1 iuc-eptacle for the` charge; ii'ieiiiisfoi' lizitiigiV the Charge with gas 0i' oil; means 'For limiting tlieirliaig electrically; iiiiziiis iiifiiiviicml liy :iii effectiveincrease in iliv elimti'ii" lient iiig 5ml liiiiliiig tu ilci'iijiirwliv im iii nil heating; iiiiil iidiiistiililfi iiiiiiii` iuiitiuliiiglie fiiiictinriiiig 0f amil l:i:i-iiiif-iitioiivcl iiiiiiins.

il. In a inciting Ji'iiiiiiiciv= iliij iiiiiiiiiiizitiiiii uf iicliuiiibeieii f'iiiiiucv liiiilji' 'i iiiiiiig' ii i'ur cvptzicl@ forthe charge: iiifsiiiis fm' iieiitiii;iv iiliif charge with gas Oi* Oil:iii eliUti'iiiil limiting element disposed within iiiii liiiiiiig:ii'vii ril said gais, iii'- iiiil iiiid having :i iivggjiil iw tviiiAiiiii'aiili'v risisi-iiiice iiiellii-iiiiil: iiioziiw im liiiiiiii'i5gflie, @liiiiim iflQi-*iiiiifiiij-g niiiil iiliiiiiiii living!iiiiiimriiiil iii iliix iiiviiii :iiiiil ifili iiimil iiilaiiiiigLiiioaiiii; iiiiiiiiis iiiiiiiiiiiiril by iiii iilfeClii'v increase isivfliwiiv lii'fiitiiig iiiirl iiiiliiig; to defiiiimi ifiiel Sli wiiiig;

l'iiiici911" iv

